Vibration Acquisition with NI USB-9234 using NIDaqMxBase library

[giaulo]

I have a NI USB-9162 connected with a NI-9234 correctly configured and installed under OpenSUSE 11.3. This is the ldaq output:

>lsdaq 
--------------------------------
Detecting National Instruments DAQ Devices
Found the following DAQ Devices:
NI USB-9234: "Dev1"    (USB0::0x3923::0x72B5::0164852A::RAW)
--------------------------------

I'm developing a simple application to acquire the vibration values of an oject connected with an accelerometer.
I start from the acquireNScans-AnlgStart.c example from the NIDaqMxBase 3.4.5 documentation.

Unfortunately the program fails and produces the following error:

"DAQmxBase Error -200428: Value passed to the Task/Channels In control is invalid."

Then I realize that the NI9234 doesn't support analog and digital triggers so I decided to try with the acquire1Scan.c (one scan without trigger):

int main(int argc, char *argv[])
{
    // Task parameters
    int32       error = 0;
    TaskHandle  taskHandle = 0;
    char        errBuff[2048]={'\0'};

    // Channel parameters
    char        chan[] = "Dev1/ai0";
    float64     min = -10.0;
    float64     max = 10.0;

    // Timing parameters
    uInt64      samplesPerChan = 1;

    // Data read parameters
    float64     data;
    int32       pointsToRead = 1;
    int32       pointsRead;
    float64     timeout = 10.0;


    DAQmxErrChk (DAQmxBaseCreateTask("",&taskHandle));
    DAQmxErrChk (DAQmxBaseCreateAIVoltageChan(taskHandle,chan,"",DAQmx_Val_Cfg_Default,min,max,DAQmx_Val_Volts,NULL));
    DAQmxErrChk (DAQmxBaseStartTask(taskHandle));
    DAQmxErrChk (DAQmxBaseReadAnalogF64(taskHandle,pointsToRead,timeout,DAQmx_Val_GroupByChannel,&data,samplesPerChan,&pointsRead,NULL));

printf ("Acquired reading: %f\n", data);

Also this program fails and gives this error:

DAQmxBase Error -200077: <err>Requested value is not a supported value for this property. (Timing Mode)

How can I acquire at least a single data value from the accelerometer from this devices using the NIDaqMxBase API?

[Steven_K. · Accepted solution]

Hi giaulo,

The examples that you tried to run are not compatible with your device.

The 9234 does not support analog triggering so the "acquireNScans-AnlgStart.c" examples will not work. 

It is also unable to do a single point acquistion since is built on a delta-sigma ADC architecture. Here is a knowledgebase article explaining the limitation:

KB 4SU94SH7: Does DSA Hardware Support Single Point Acquisition?

This is the reason why the "acquire1Scan.c" doesn't work.

You will need to run an example that does a buffered acquisition. "acquireNScans.c" would be a good one to look at. Be aware for all of these examples, the default input range is +/-10V. The 9234 can only input +/-5V, so there will need to be some modifications. Also since you are trying to read from an accelerometer, IEPE excitation will likely be needed. I've attached an example that is based off of "contAcquireNChan.c" example that correctly sets the range and enables excitation for that device.

[giaulo]

Thank you! Now I'm able to acquire data.